Optical disc device

Abstract

Even when a first differentiation value is equal to or greater than a first threshold value, this optical disc device does not confirm “CD” to be the differentiation result, as long as a first focus error signal FE 1 or a first focus sum signal FS 1 is less than a second threshold value; and even when the first differentiation value is equal to or greater than a second differentiation value, this optical disc device does not confirm “CD” to be the differentiation result, as long as the signal FE 1 is less than a second focus error signal FE 2 , or as long as the signal FS 1 is less than a second focus sum signal FS 2 . The signals FE 1 and FS 1 are obtained when a CD laser beam is directed onto an optical disc. The signals FE 2 and FS 2 are obtained when a DVD laser beam is directed onto the disc.

What is claimed is: 
     
       1. An optical disc device, comprising:
 an optical pickup for directing light onto an optical disc, as well as detecting returning light from the optical disc by a photodetector; 
 a focus error signal generator for processing an electrical signal outputted from the photodetector and generating a focus error signal; 
 a focus sum signal generator for processing an electrical signal outputted from the photodetector and generating a focus sum signal; and 
 a differentiator for differentiating whether the optical disc is a CD or a DVD; and 
 wherein, in the event that a differentiation result fails to be confirmed in both a CD confirmation process and a DVD confirmation process, the differentiator performs a final confirmation process; 
 and wherein, in the CD confirmation process, 
 in a case in which a first differentiation value in accordance with a ratio of a first focus error signal, which is a focus error signal generated by the focus error signal generator when the optical pickup directs a CD laser beam onto the optical disc, to a first focus sum signal which is a focus sum signal generated by the focus sum signal generator when the optical pickup directs a CD laser beam onto the optical disc, is equal to or greater than a first threshold value, and moreover in which the first focus error signal or the first focus sum signal is equal to or greater than a second threshold value, the differentiator confirms “CD” to be the differentiation result; 
 in the DVD confirmation process, 
 in a case in which a second differentiation value in accordance with a ratio of a second focus error signal, which is a focus error signal generated by the focus error signal generator when the optical pickup directs a DVD laser beam onto the optical disc, to a second focus sum signal which is a focus sum signal generated by the focus sum signal generator when the optical pickup directs a DVD laser beam onto the optical disc, is equal to or greater than a third threshold value, the differentiator confirms “DVD” to be the differentiation result; and 
 in the final confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the second differentiation value, and moreover in which the first focus error signal is equal to or greater than the second focus error signal, or the first focus sum signal is equal to or greater than the second focus sum signal, the differentiator confirms “CD” to be the differentiation result. 
 
     
     
       2. The optical disc device of  claim 1 , wherein
 in the CD confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the first threshold value, a determination is made as to whether or not the first focus error signal or the first focus sum signal is less than the second threshold value. 
 
     
     
       3. The optical disc device of  claim 1 , wherein
 in the final confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the second differentiation value, a determination is made as to whether or not the first focus error signal is less than the second focus error signal, or as to whether or not the first focus sum signal is less than the second focus sum signal. 
 
     
     
       4. The optical disc device of  claim 2 , wherein
 in the final confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the second differentiation value, a determination is made as to whether or not the first focus error signal is less than the second focus error signal, or as to whether or not the first focus sum signal is less than the second focus sum signal. 
 
     
     
       5. The optical disc device of  claim 1 , wherein
 in the CD confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the first threshold value, and moreover in which the first focus error signal is equal to or greater than the second threshold value, the differentiator confirms “CD” to be the differentiation result; and 
 in the final confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the second differentiation value, and moreover the first focus error signal is equal to or greater than the second focus error signal, the differentiator confirms “CD” to be the differentiation result. 
 
     
     
       6. The optical disc device of  claim 2 , wherein
 in the CD confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the first threshold value, and moreover in which the first focus error signal is equal to or greater than the second threshold value, the differentiator confirms “CD” to be the differentiation result; and 
 in the final confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the second differentiation value, and moreover in which the first focus error signal is equal to or greater than the second focus error signal, the differentiator confirms “CD” to be the differentiation result. 
 
     
     
       7. The optical disc device of  claim 3 , wherein
 in the CD confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the first threshold value, and moreover in which the first focus error signal is equal to or greater than the second threshold value, the differentiator confirms “CD” to be the differentiation result; and 
 in the final confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the second differentiation value, and moreover in which the first focus error signal is equal to or greater than the second focus error signal, the differentiator confirms “CD” to be the differentiation result. 
 
     
     
       8. The optical disc device of  claim 4 , wherein
 in the CD confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the first threshold value, and moreover in which the first focus error signal is equal to or greater than the second threshold value, the differentiator confirms “CD” to be the differentiation result; and 
 in the final confirmation process, 
 in a case in which the first differentiation value is equal to or greater than the second differentiation value, and moreover in which the first focus error signal is equal to or greater than the second focus error signal, the differentiator confirms “CD” to be the differentiation result.